Illustrated herein in embodiments are development apparatuses for ionographic or electrophotographic imaging and printing, and more particularly, endless seamed electrostatic development belts comprised of at least two layers and joined by an overlapping seam. When electrodes are incorporated, the belt can be used to charge and transport toner on the surface thereof and to form a toner cloud in the development zone for the development of a latent electrostatic image.
In this regard, the process of electrophotographic imaging and printing includes charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive surface is exposed to alight image of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface. After the electrostatic latent image is recorded on the photoconductive surface, the latent image is developed by bringing a developer material into contact with the image.
Two-component and single-component developer materials are commonly used in the development process. A typical two-component developer material comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single-component developer material typically comprises only toner particles. In either type of material, the toner particles are attracted to the latent image and form a toner powder image in the vicinity of the photoconductive surface. Under the influence of the image field, the toner is developed onto the photoconductor. The toner powder image is subsequently transferred to a substrate such as a copy sheet. The toner powder image is then heated to permanently fuse it to the substrate.
The electrophotographic development process noted above can also be modified to produce color images. One color electrophotographic development/marking process, called image-on-image processing, superimposes toner powder images of different color toners onto the photoreceptor prior to the transfer of the composite toner powder image onto the substrate. While the image-on-image process is beneficial, it has several problems. For example, when recharging the photoreceptor in preparation for creating another color toner powder image it is important to level the voltages between the previously toned and the untoned areas of the photoreceptor. This requires an additional process step that can affect subsequent development steps as well as the print quality of the resultant print.
Single-component development systems typically use a donor member for transporting charged toner to the development nip defined by the donor member and a photoconductive member. The toner is developed on the latent image recorded on the photoconductive member by a combination of mechanical and/or electrical forces.
Scavengeless development and jumping development are two types of single-component development. A scavengeless development system uses a donor member with a plurality of electrodes closely spaced therefrom in the development zone. An AC voltage is applied to the electrodes forming a toner cloud in the development zone. The electrostatic fields generated by the latent image attract toner from the toner cloud to develop the latent image.
In jumping development, an AC voltage is applied to the donor member, detaching toner from the donor member and projecting the toner toward the photoconductive member so that the electrostatic fields generated by the latent image attract the toner to develop the latent image. Single-component development systems offer advantages in low cost and design simplicity, but the achievement of high reliability and simple economic manufacturability continue to present problems.
Additionally, the donor member is frequently in the form of a flexible electrostatic development or donor belt. These belts can be formed by cutting a rectangular, a square, or a parallelogram shape sheet from a web containing at least one layer of thermoplastic polymeric material. Opposite ends of the sheet are then overlapped and joined together by compression and ultrasonic, adhesive, or thermal bonding to form a seam. When compression is combined with thermal bonding, the process for securing the seam is referred to as molding. When compression is combined with an adhesive(s) to secure the seam this process is referred to as adhesive bonding. The seam typically extends from one edge of the belt to the opposite edge.
Generally, these donor belts comprise at least a supporting substrate layer and at least one layer comprising a thermoplastic polymeric material. However, it has been found that, during extensive cycling, the seam area may break down due to fatigue, etc., thereby shortening the service life of the donor belt.
Therefore, there is a need to provide seamed flexible donor belts with an improved seam morphology which can withstand greater dynamic fatigue conditions thereby extending belt service life. Furthermore, there is also a need for donor belts having improved seam designs that are thin in seam profile, resistant to seam cracking/delamination, substantially free of seam protrusions, and have improved seam region physical and electrical continuity.